by Physicians, Scientists, and Engineers for Healthy Energy

Category Archives: shale gas

FACT: While hydraulic fracturing has been used in energy development since the late 1940s, uncconventional development of gas using high volume, slickwater fraccing from long laterals with multi-well pads and clustered drilling has only become possible since ~2007 and is still being developed. The differences between conventional “fracking” and the new suite of technological advancements, as well as impacts of this much more intensive practice, is explained in detail here.

FACT: In 2010 and 2011, the EPA substantially revised and increased their estimates of methane emissions from natural gas systems. As of the end of 2011, the most recent EPA data indicate leak rates of 2.5% for conventional natural gas and 3.9% for shale gas (details of calculation here) over the full life-cycle. A recent field study of methane emissions from an unconventional gas field in Colorado suggests the EPA estimates may be low.

FACT: The best and most recent science indicates that methane is 33 times more powerful than carbon dioxide as a greenhouse gas, when considered over an integrated time period of 100 years following emission, and 105 times more powerful on an integrated 20 year time period.

The global warming potential or GWP, is a simple metric often used to assess how much more powerful a given greenhouse gas is when compared to carbon dioxide. Back in 1996, the Intergovernmental Panel on Climate Change estimated the GWP for methane as 21, considered over a 100-year time period following emission. As of 2007, the IPCC presented global warming potentials (GWP) for methane of 25 for a 100-year integrated time-frame and 72 for a 20-year integrated time frame after emission. Using a more recent model to better capture how methane interacts with other radiatively active substances, Shindell et al. in a 2009 paper in Science updated these factors to 33 and 105 respectively. These higher values reflect the best, most current science. The GWP for methane is less at the longer time scale simply because methane does not stay in the atmosphere for as long as carbon dioxide.